- Cohort 3 (for patients in need of immediate interleukin-2 [IL-2] and those with disease progression after treatment in cohorts 1 or 2): Patients receive fowlpox vaccine either IV or IM* once every 4 weeks for 4 doses and IL-2 IV every 8 hours for a maximum of 12 doses beginning 24 hours after fowlpox vaccine.